FI74358C - KAPASITIV LAESMETOD FOER KODKORT OCH LAESANORDNING FOER FOERVERKLIGANDE AV FOERFARANDET. - Google Patents

Description

! 74358

A code card capacitive locking method and a reading device for implementing the method. - Kapasitiv läsmetod för kodkort och läsanordning för förverkligande av förfarandet.

The invention relates to a capacitive reading method of a code card, in which the reader's transmitter electrodes transmit a high frequency signal over a slot reserved for the card to receiver electrodes on the opposite side of the slot, the received signal of which changes due to conduction spots on the card. The invention also relates to a code card capacitive reader for carrying out the method, comprising a high-frequency generator, transmitter electrodes connected to a generator for transmitting a high-frequency transmitter signal, receiver electrodes opposite the transmitter electrodes, the transmitted signal changes due to the conduction spots on the card.

In known code card readers of this type, the identification of the code card in the static position of the card is performed only after the card has been inserted all the way into the receiving slot of the reader. Such a code reading principle limits the number of code combinations on the card to a rather modest relative to the number of transceiver electrode pairs of the reader. It is clear that as the number of transceiver electrode pairs increases, the price of the device increases correspondingly. Another serious drawback of known capacitive card readers is their susceptibility to interference and the resulting unreliability. However, such code card readers are used in application areas where very high reliability and in addition a large number of code combinations are required. Such code cards and their readers are becoming more common for activating a wide variety of automatic devices such as unlocking, credit card machines such as petrol stations, bank cards such as ATMs, etc. As the above

It is an object of the invention to provide an improved code card capacitive reading method and reader that achieves the largest possible number of code combinations that can be reliably identified with as few transceiver electrode pairs as the reader.

This object is achieved by the invention by means of the features set out in the appended claims.

In the following, an embodiment of the invention will be described in more detail with reference to the accompanying drawings, in which Fig. 1 shows a top-read code card.

Figure 2 shows the placement of capacitive identification electrodes in a card reader.

Fig. 3 shows a cross-section of the code reading electrodes of the reading device and Fig. 4 shows the signals of the different electrodes of Fig. 3.

Figure 5 shows in cross-section the structure and mutual placement of the positioning electrodes of the reading device and the preamplifiers associated with the receiver electrodes associated with the signal processing circuit 10.

Figure 6 shows the detection area A of the card positioning electrodes and the detection area B of the code reading electrodes with respect to the movement of the card over the distance S.

The card reader is intended to read a card 1 according to the 86 x 54 mm "access card standard" made of plastic. This column has a single positioning spot 3. The other four rows have 31 code spots 2. The code is formed when a certain part of the code spot is formed as electrically conductive spots. It is found that e.g. a huge number of code combinations are achieved with the 31 code spots shown. A blank area 4 is left at the front edge of the card and there are conduction spots 5 at the back edge to indicate a possible incorrect position of the card.

Figure 2 shows the arrangement of the electrodes of the card reader 11. The position of the card 1 relative to the reader 11 is read by eight pairs of electrodes 13, the structure of which will be explained later in connection with Fig. 5. The electrodes 12 for reading the code are arranged in parallel in one row, which is transverse to the pushing direction of the card 1. There are four code reading electrodes 12 corresponding to the number of rows of code dots 2.

The electrically conductive code dot on card 1 is capacitively read by the sensor shown in Figure 3. The sensor transmitter side electrodes 12a and 12b from the generator is brought to 5 V p-p of about 500 kHz square wave. The phase inverter 7 inverts the phase of the signal f on the electrode 12a with respect to the phase of the signal on the electrodes 12b (cf. Fig. 4).

When there is no conductive code dot 2 between the electrodes, the signal is capacitively coupled to the receiver electrode 12, from which the signal obtained is amplified in the preamplifier 9 e.g.

5 V level. The received signal f2 is slightly (TQ) delayed from the transmitted signal f1 due to the slowness of the amplifier 9.

When a card 1 with a conductive code dot 2 is inserted into the gap between the electrodes, the dot 2 comes to a point where it partially or completely covers the receiver electrode 12. In this case, the overlapping area of the electrode 12b and the dot 2 is larger than the overlapping area of the dot 2 and the electrode 12a. area. The signal from the electrode 12b is coupled to the dot 2 4 74358 and from there to the receiver electrode 12, whereby the phase of the signal f2 is reversed by about 180 ° with respect to the ft. The detection of spot 2, i.e. the inversion of the ^ 2in phase, is expressed by sampling the signal f2 at the rising edge of the signal. Thus, the output data is "1" when the conductivity spot 2 is not in between and otherwise "0".

The structure of the electrodes used to determine the position of the card differs slightly from the sensor for reading the code range. It can be seen from the cross-sectional view of Figure 5 that the successive transmitter electrodes 13a and 13b are in different phases with each other because they alternate and the signals. The signal ϊγ from the generator G is converted by the phase inverter 7 into a signal f ^. The receiver electrodes 13 have a small surface area and are located at the leading edge of each transmitter electrode 13a and 13b as seen in the pushing direction of the card. In addition, between the receiver electrodes 13 are ground electrodes 13c. When the card is inserted into the gap between the electrodes, the conductivity spot 3 of the card for position determination comes on the electrode 13, whereby the phase of the received signal f2 is reversed. This is because the overlapping area of the spot 3 and the previous transmitter electrode 13b is larger than the overlapping area of the transmitter electrode 13a on the spot 3 and the receiver electrode 13.

The phase of the received signal ^ 2 is reversed when the dot 3 comes more under the transmitter electrode 13a on the receiver electrode 13.

With this electrode structure, a narrower conduction spot detection area A (Fig. 6) is provided than the detection area B of the code reading electrodes 12. In this way it can be ensured that when the card positioning spot 3 is detected, the possible the code spots in the cross row are certainly detected and the data indicating the code of that row, e.g. "1 1 0 1" is obtained correctly regardless of the speed and direction of movement of the card 1. The practical speed range of the card is 0 ... 50 m / s.

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The preamplifiers 8 and 9 of the receiver electrodes can be made, for example, from non-buffered inverters of the CMos series.

The data signal processing unit 10 can be constructed from ready-made IC circuits in a manner known from digital technology. The structure of the processing circuit 10 depends essentially on the application.

Claims (4)

1. Capacitive code card reading method, in which method a high frequency signal is transmitted with the transmitter electrodes (12a, 12b; 13a, 13b) of the reading device (11) over a read slot provided for the code card (1) to receiver electrodes (12; 13) opposite side, where the received signal varies under the influence of conductance dots (2; 3) present in the code card (1), the position of the card (1) being determined several times during the displacement movement occurring in the reading slot and the card's code-forming conductance cracks (2) are read in a transverse row relative to the code card's sliding direction during each positioning, characterized in that the transmitter electrode portions of the detector electrodes (12a and 12b; , in different known modes, signals (f 1 and f 3) are transmitted in different phases, which, by sliding the card (1) between the e-electrodes, are connected in turn by switching the cone of the card duct cracks (2; 3) in the respective case to the same receiver electrode (12; 13), that the phase of each of the receiver electrode (12; 13) received signal (f2) is examined in relation to the phase of the transmitter signal (f eller or f)) and the phase change is indicated such as a conductance crack (2; 3) read in the card. 2. Capacitive code card reading device for performing a method according to claim 1 or 2, wherein said device includes a high frequency generator, transmitter electrodes (12a, 12b; 13a, 13b) coupled to a generator for transmitting a high frequency transmitter signal, opposite the transmitter electrode receiver electrodes (12; 13), forming a reading slot between the transmitter and receiver electrodes, in which a code card (1) can be inserted so that the capacitively passing signal between the electrodes changes under the influence of the conductor cracks (2: 3) in the card (1), where the code-forming conductance cracks (2) lie in several rows to form a multi-line code and the code reading electrodes (12a, 12b, 12) lie only at the beginning end of the reading slot